Color photography.



ALBERT DAVIES, OF STONEHOUSE, PLYMOUTH, ENGLAND.

Specification of Letters Patent.

COLOR PHQTOGRAPHY.

Patented .Feb; 18, 1908.

Application filed March 12. 1907. seal No. 361.894.

To all whom it may concern:

Be it known that I, ALBERT DAVIES, photographer, a subject of the King of Great Britain, residing at 65 Durnford street, Stonehouse, Plymouth, in the county of Y Devon, England, have invented certain new .and useful Improvements in Color Photog' raphy, and I-do hereby declare the following to be a full, clear, and exact description of they invention, such as will enable others skilled in the" art to which it appertains to make and use the same.

This invention relates to improvements in theproduction of colored photographs from superimposed primary colored carbon tissues and has more particular reference to the process of preparing and obtaining the blue -colors, and halftones, of a more suitable and permanent character than heretofore, and the interdependent process of hardening the transfer papers, their separation from the negative plates and superimposition .upon one another to obtain accurate register of the individual prints. It is carried out as follows :-According to usual methods negatives of colored objects are taken through light filters or screens on platessensitive to color. The negatives are printed on carbon tissues of suitable red, blue and yellow pigments, and the resulting images are then developed and superimposed on one support. In this process owing to the irregular stretching of transfer paper great difficulty is experienced in causing the prints to exactly coincide. According to this invention thisdifficulty is overcome by hardening the gelatin transfer paper as a whole (as distinguished from merely using paper coated with hardened gelatin), before the prints are put upon it and by mounting the prints as has beforebeen proposed on temporary rigid backings while they are being tr ansferred to the paper. According to this invention also I employ a blue coloring matter consisting'of a mixture f Prussian blue and picric acid which turns :blue into a blue green, which color will assimilate much better with the yellow and red than the ordinary blue and is much more permanent than the anilin colors commonly employed.

The following description applies to a three color photograph. bon tissues in about three per cent. solution of bichromate of potash for three minutes and then hang them up to dry. The red andyellow tissues are those ordinarily employed,

I sensitize the car-1 but the blue tissues should be, prepared with Prussian blue (Turnbulls blue). To the blue sensitizing bath I add about four ounces of a concentrated solution of picric acid to eighty ounces of about a three cent. solution of bichromate of potash, or the 'picric acid may be added to the blue emulsion when making the tissue, or the blue print can be manipulated with a solution of picric acid while on the glass plate to improve the half tones of the picture. All the tissues should be dried in an airtight calcium chlorid box and heat should not be used.

Positive prints are obtained upon the carbon tissues from the color negatives in the ordinary manner. The tissues are then soaked in cold water until limp, and are transferred to glass plates which have beenrubbed with French chalk and then coated with collodion which has been allowed to set but not to dry and has been washed in clean water. Or the French chalk may be replaced by a mixture of asbestos and talc, or of carbonate of magnesia, and arrowroot. Care must be taken not to put too much pressure on the squeegee used in transferring the tissues to the plates. Aftera few minutes the plates with the tissues on themzare soaked in hot water 100 Fahrenheit for a few minutes and the paper on the back of the tissue is removed. The prints are then developed and washed. The yellow rint is fixed'by means of a weak solution of ormalin, or a solution of alum may be used if desired. The blue and red prints should only be fixed in a weak solution of formalin and simply well washed and u'tto dry. Any good white or tinted dou fe transfer gelatin coated pa er,-is suitable for the final support of the nuts. The transfer paper is soaked in colr water for a few minutes, then in about a ten per cent. solution ofalum (or a weak solution of formalin) for one minute and is well washed, and is placed upon the yellow print while it is still wet and the two are well squeezed together. When the yellow print has become dry, it

the glass plate by a sharp knife. The yellow ,print having been successfully transferred the next 'step taken is with the blue one. Both the red and blue prints are transferred from the glass plates in the same manner but a solution consisting of one part by weight of Placamia Zz'chenoides in 400 parts of water is desirable to insure adherence. The solution is strained and used at a temperature not over 95 Fahrenheit. The blue print while still" on the glass backing is laced one levelstand "and the solutlon 1s poured ove'r it.

yellow print previously soakedin cold water is placed on the top ofit and then slightly. squeezed. The twoprints can be registered by looking through the lass of the blue print. The prints are drie on-the glass plate and are then separated from it as The red print 1s transferred in before.

It is ferred to paste a piece of double transfer paper which has been soaked in alum (or ormalin) water and then washed, to the back of the aper of final support while on the glass p ate with the gelatin outside. This will kee the finished print flat when it is detache from the glass. If any of the three prints appear to be too dense when temporarily superim osed they can, if not over printed, be re need by gently rubbing with cotton wool and methylated spirits.

I do not bind myself to superimpose the pigment tissues in the order mentioned, for instance in making transparencies it is better to place the blue first the yellow second and the red last but in any case .the operator can" decide which order will best suit the object.

. Since the blue pigment tissue produces the shades and dark eifects in any given picture it followsthat in this particular color it is of the utmost importance that it not only be permanent but assimilate well with the other colors, and I have found that these qualifications are satisfied when it is prepared as above indicated, besides giving the operator full power to enhance or depress any portion of the picture by stippling with the picric acid solution when the blue tissue is on the plate. i

What I claim is:

-1. The process of producing colored photographs, which consists in first printing the same icture o'n sensitized pigment tissues of d' erent colors, then attaching the said tissues to prepared plates, then removing the paper from the backs of the tissues and develo ing and fixing the ictures while on the sald plates, and final y superimposing the said pictures on a single sheet of transfer paper.

- 2. The process of producing colored pho tographs, which consists in first printing the same picture on sensitized pigment tissues of different colors, then attaching the said tissues to pre ared lates, then removing the paper from t e bac s of the tissues and defthe papers with collodion, t

of difl'erent colors, then attac velop" and fixingthe pictures while on the said p lgtes, and finally superimposing the fixed ic'tures upon a single sheet of gelatin transf er paper which has been hardened before a lying the. pictures toit.

3. I e process of producing colored photographs, which consists in print' the ent tissue whic .has

picture on blue p' een treated with PICIIC acid and bichromate of potash, and printing the same picture on sensitized igment tissues of other colors, then attacfiling' the said tissues to fprepared plates, then removing the paper om the acks of the tissues and develo and fix.-'

ing the pictures while on the sald p ates, a'nd finally superimposing the said pictures on a single sheet of transfer paper.

4. The process of producing colored photographs, which consists in first printing. the same picture on sensitized p' ment tissues of diiferent colors, then attac tissues to repared plates, then removing developing and fixing the pictures while on the. said plates, reducing any picture which om the backs of the tissues and the said is too thick by rubbing it with spirits before removing it from its plate, and finally su er-' imposing the saidpictures on a single s eat of transfer paper.

5. The process of producing colored photographs, which consists in first printing the same pictureon sensitized pigment tissues of difierentcolors,.then attaching the said tissues to glass plates which have been treated with chalky material and then coated en removing the paper fromthe backs of the tissues and developmg :and fixing the ictures while on the said plates, and fina ly superimposing the said -p1ctures on a'single sheet of transfer paper.

'6. The process of producing colored photographs, which consists in first printing the same picture on sensitized pi ent tissues figthe said tissues to prepared plates, then removing the paper from the backs of the tissues and deve oping and fixing the ictures while on the said plates, then trans erring one of the said pictures onto a sheet of gelatin transfer paper, treating the said sheet and picture with an adhesive solution, and superimposing the remaining pictures onto the said sheet.

In testimony whereof I affix my signature in presence of two Witnesses.

ALBERT DAVIES. Witnesses:

E. YOUNGS', W. WALKE. 

